The present invention relates to a clamp for clamping a mandrel onto a cylindrical body to provide intimate contact between the mandrel and the body, and particularly for clamping a heater onto the exterior of an injection molding nozzle.
Cylindrical heater assemblies are clamped onto injection molding nozzles for insuring good thermal conduction from the heater to the nozzle to maintain the temperature of the nozzle at an adequate level. The heaters and nozzles require periodic maintenance and replacement, and thus it is desirable to have the ability to easily remove the heater from the nozzle for maintenance. The heaters and nozzles are generally recessed in a cavity so the ability to clamp and release the heater easily without operating mechanism within the cavity is desirable.
In the past many types of heater clamps have been advanced, including thermal clamps which were designed to automatically clamp onto the injection molding nozzle as the temperature of the heater increased. Prior art thermal clamps have had a spool or mandrel on which a heater is mounted, with the spool or mandrel having a bore large enough to slip over the heater nozzle. The heater may be surrounded by an outer housing that is also cylindrical, and which has a different coefficient of thermal expansion from the spool. The concept of this type of device was to provide for radially inward clamping because of the differential in expansion between the heater mounting spool or mandrel and other components, to cause the mandrel to tighten down onto the surface of the nozzle for heat transfer purposes.
The amount of differential thermal expansion in a radial direction is many times insufficient to provide an adequate clamping force onto the injection molding nozzle when the mandrel bore is large enough so it can be slipped over the nozzle.
The present invention utilizes a longitudinal actuated camming arrangement for tightening the mandrel on which the heater is mounted onto a body using mechanical or thermally caused longitudinal differential movement between mandrel and an outer housing.